Apparatus and method for defrosting components in a transport refrigeration unit

ABSTRACT

A transportation refrigeration unit, which is configured to defrost the evaporator coil of an evaporator, is provided with improvements to a power transfer mechanism. The power transfer mechanism incorporates a coupling mechanism that can transfer power from the condenser fan to the evaporator fan. In one embodiment, the coupling mechanism is encapsulated in a housing, which forms an interior cavity for receiving a lubricating fluid therein. The interior cavity is such that the coupling mechanism is immersed in the lubricating fluid.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent Application Ser. No. 61/353,357 entitled “Apparatus and Method for Defrosting Components in a Transport Refrigeration Unit” filed Jun. 10, 2010, the content of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates generally to refrigeration systems, and more particularly, to embodiments of a transportation refrigeration unit configured to defrost evaporator coils without affecting temperature of a controlled environment cooled by the transportation refrigeration unit.

BACKGROUND

Mobile refrigeration systems are commonly used for cooling and sometimes heating railroad refrigeration cars, trucks, and containers. To facilitate implementation of the relevant cooling cycles, these refrigeration systems often couple working components such as fans to the drive mechanism, e.g., the engine, of the respective transportation vehicle. This configuration is often employed by way of a mechanical drive between the engine and the refrigerant compressor, condenser fan, and evaporator fan. This drive may include various components, including clutches that can disengage the evaporator fan to permit the evaporator to be defrosted without warming the contents of the container.

SUMMARY

There is provided below embodiments of a transportation refrigeration unit that disengages the evaporator fan, but that is configured so as not to require additional hardware. The improvements disclosed herein can improve reliability by effectuating in a single component the operative engagement and disengagement of the evaporator fan.

By way of example, and as discussed in more detail below, in one embodiment, in a transportation refrigeration unit of the type for conditioning the environment interior of the trailer, said transportation refrigeration unit including an evaporator fan, a condenser fan, and a power transfer mechanism for simultaneously driving the evaporator fan and the condenser fan, the power transfer mechanism further comprises a primary fan shaft coupled to the condenser fan, a secondary fan shaft aligned with the primary shaft, the secondary shaft coupled to the evaporator fan, a coupling mechanism coupling the primary fan shaft and the secondary fan shaft, a fanshaft housing in surrounding relation to the coupling mechanism, and a lubricating fluid disposed in the fanshaft housing.

In another embodiment, a power transfer mechanism for use on a transportation refrigeration unit of the type for conditioning the environment interior of the container, the transportation refrigeration unit including an evaporator fan and a condenser fan, said power transfer mechanism comprises a coupling mechanism coupling a condenser fan shaft and an evaporator fan shaft, the condenser fan shaft coupled to the condenser fan and imparting rotation to the evaporator fan shaft through the coupling mechanism. The power transfer mechanism also comprises a fanshaft housing comprising a first portion and a second portion coupled together in a manner forming a interior cavity about the coupling mechanism. The power transfer mechanism further defined wherein the interior cavity is sealed so as to maintain a volume of a lubricating fluid therein, and wherein the coupling mechanism is immersed in the lubricating fluid.

In yet another embodiment, a transportation refrigeration unit comprises a vapor compression refrigeration system comprising a compressor, an evaporator with an evaporator fan, and a condenser with a condenser fan. The transportation refrigeration unit also comprises a fanshaft coupled to the condenser fan and the evaporator fan, the fanshaft comprising a first shaft secured to the evaporator fan, a second shaft secured to the condenser fan, and a fanshaft housing in surrounding relation to an integrated coupling mechanism communicating rotational motion between the first shaft and the second shaft. The transportation refrigeration unit further defined wherein the fanshaft housing forms an interior cavity about the integrated coupling mechanism. The transportation refrigeration unit further defined wherein the interior cavity is sealed so as to maintain a lubricating fluid therein.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention briefly summarized above, may be had by reference to the embodiments, some of which are illustrated in the accompanying drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. Moreover, the drawings are not necessarily to scale, emphasis generally being placed upon illustrating the principles of certain embodiments of invention.

Thus, for further understanding of the concepts of the invention, reference can be made to the following detailed description, read in connection with the drawings in which:

FIG. 1 is a schematic illustration of an example of a refrigerant vapor compression system;

FIG. 2 is a side, schematic illustration of an exemplary embodiment of a transportation refrigeration unit with a power train mechanism compatible with the refrigerant vapor compression system of FIG. 1; and

FIG. 3 is a side, cross-section of a fanshaft for incorporation into the power train mechanism of a transportation refrigeration unit, such as the transportation refrigeration unit of FIG. 2.

DETAILED DESCRIPTION

A transportation refrigeration unit is provided with a power transfer mechanism that is configured to permit interior portions of the unit to warm, while continuing to operate to cool, e.g., a volume attached thereto. These features are beneficial because operating temperatures consistent with the operation of the unit cause frost and ice to build-up on components. This build-up is detrimental to operation of the unit, and more particularly can reduce the efficiency of the refrigeration cycle needed to maintain the subject volume at its desired temperature. The power transfer mechanism in embodiments of transportation refrigeration units discussed below, however, is configured to facilitate melting of the frost and ice without impacting the desired temperature. Moreover, unlike conventional systems in which separate mechanisms and drive systems are required to cause warming to occur, the transportation refrigeration units of the present disclosure incorporate into a single drive the functionality necessary to facilitate melting, and thus improve the performance of the transportation refrigeration unit without the addition of components and cost associated therewith.

These and other concepts are described in connection with FIGS. 1-3 below. For purposes of clarity, and to facilitate the pending discussion, an exemplary refrigerant vapor compression system 100 is illustrated in the schematic diagram of FIG. 1. The system 100 is typical of the transportation refrigeration units discussed above and contemplated herein. The system 100 includes a condenser 102 such as an air-cooled condenser with a condenser coil 104 and a condenser fan 106. Typically the condenser coil 104 comprises tubes and/or fins designed to improve the transfer of heat from the refrigerant gas to the air. The system 100 also includes an evaporator 108, and in the present example the evaporator 108 includes and evaporator fan 110 and evaporator coils 112 through which refrigerant can flow. The system further includes an internal combustion engine 114 such as diesel truck engine and a compressor 116 such as a reciprocating compressor. The internal combustion engine 114 drives the condenser fan 106, the evaporator fan 110, and the compressor 116, wherein in one example operation of the compressor 116 raises the pressure and the temperature of refrigerant gas as the refrigerant gas is forced into the condenser 102.

The condenser fan 106 circulates surrounding air over the outside of the condenser coil 104, which removes latent heat from the refrigerant. By removing the latent heat from the refrigerant gas, the refrigerant gas condenses to a liquid. The system 100 also includes a receiver 118, which provides storage for excess liquid refrigerant during low temperature operation. A filter-drier 120 can be provided in which an absorbent is used to keep the refrigerant clean and dry. Heat dissipation from the liquid if further enhanced by way of a sub-cooler unit 122 and a heat exchanger 124, both of which are configured to facilitate further cooling of the passing refrigerant liquid.

Referring now to FIG. 2, and also to FIG. 1, systems such as the system 100 are implemented as part of transportation refrigeration units, such as the exemplary transportation refrigeration unit 200 that is depicted in FIG. 2. In this embodiment, the unit 200 includes primary components such as a condenser 202 that has a condenser coil 204 and a condenser fan 206 for drawing air into the condenser 202. The unit 200 also includes an evaporator 208 with an evaporator fan 210 and evaporator coils 212, which may be subject to the problem of frost and ice build-up. An internal combustion engine 214 is provided, which is coupled to the condenser fan 206 and to the evaporator fan 210. The transportation refrigeration unit 200 is coupled to a container 216 such as a temperature controlled environment that is found on a cargo box of a refrigerated transport truck, trailer or container. The concepts disclosed herein are likewise applicable to a display case, merchandiser, freezer cabinet, cold room or other perishable/frozen product storage area in a commercial establishment. In other implementations of the transportation refrigeration unit 200, the container 216 may be a climate controlled comfort zone within a residence, office building, hospital, school, restaurant or other facility.

In the present example, the transportation refrigeration unit 200 also includes a power transfer mechanism 218, which couples the internal combustion engine 214 to the condenser fan 206 and to the evaporator fan 210. The power transfer mechanism 216 may include a fanshaft 220, and in its present configuration the fanshaft 220 may include an evaporator shaft 222 and a condenser shaft 224 coupled to, respectively, the evaporator fan 210 and the condenser fan 206. The fanshaft 220 can also include a fanshaft housing 226 with an evaporator end 228 and a compressor end 230, each being configured to receive, respectively, the evaporator shaft 222 and the condenser shaft 206 therein. Inside of the fanshaft housing 226 there is provided an interior cavity 232, which is configured to retain a lubricating fluid 234 therein, and in which is disposed a coupling mechanism 236.

Power transfer mechanism 218 is generally configured to cause rotation of the condenser fan 206, thus drawing cooling air through the condenser 202 to cool the interior of the transportation refrigeration unit 200. Although not necessarily illustrated in detail in FIG. 2, components such as pulleys, belts, gears, gear trains, and related mechanical devices may be incorporated as part of the power transfer mechanism 218. These components may be coupled to the fanshaft 220, and in one configuration the condenser shaft 224 may have one or more pulleys disposed in axial engagement thereon. This configuration is suited to rotate the condenser fan 206 using one or more existing power inputs from, e.g., a diesel truck engine and/or other device that generates power suitable for turning the condenser fan 206.

The fanshaft housing 226 is constructed to enclose in surrounding relation the coupling mechanism 236. Seals such as mechanical seals, o-rings, gaskets, and related devices can be incorporated into or as part of the fanshaft housing 226. These seals can form part of the interior cavity 232, which is effectively sealed so as to prevent lubricating fluid 234 from escaping the fanshaft housing 226 during operation of the transportation refrigeration unit 200. In one embodiment, the construction of the fanshaft housing 226 effectively encapsulates the coupling mechanism 236 in the interior cavity 232, immersing the coupling mechanism 236 in the lubricating fluid 234. Such immersion takes advantage of the lubricating qualities of the lubricating fluid 234 to facilitate rotation of the components including the evaporator shaft 222, the condenser shaft 224, and the coupling mechanism 236, all of which have portions that are located in the fanshaft housing 226.

Coupling mechanism 236 is provided to control, and in one example to engage and to disengage the rotation of the evaporator fan 210. This control is important to the operation of the transportation refrigeration unit 200. As discussed above, and by way of example, there are times when continuous operation of the transportation refrigeration unit 200 causes frost build-up such as on evaporator coils 212 of the evaporator 208. Removal of this frost is necessary to maintain the efficiency of the refrigeration cycle, as well as to prevent excessive wear and mechanical failure of critical components in transportation refrigeration units of this type. However, in order that such removal occurs without adversely affecting the temperature of the air inside the trailer, operation of the other components of the transportation refrigeration unit 200 must continue. Thus to maintain the temperature in the trailer, but to effectuate a change in temperature in the transport refrigeration unit 200 that is necessary to melt the frost, the coupling mechanism 236 in one embodiment is activated to decoupled the evaporator fan 210 from the internal combustion engine 214 such as by disengaging the evaporator shaft 222 from the condenser shaft 224.

These concepts are further illustrated in the example of a fanshaft 300 that is illustrated in FIG. 3. The fanshaft 300 is compatible with various configurations of power transfer mechanisms, including the power transfer mechanism 218 of FIG. 2 above. In the present example, the fanshaft 300 includes an evaporator shaft 302, a condenser shaft 304, and a fanshaft housing 306 with an evaporator end 308 and a condenser end 310. The fanshaft housing 306 can include one more portions 312, and in the present configuration the portions 312 include an evaporator portion 314, proximate the evaporator end 308 and configured to receive the drive shaft 302 therein. The portions 312 also include a condenser portion 316 that is coupled to the drive portion 314 such as by fasteners 318, which can include screws and bolts, but can also incorporate various weld and weldment-type fasteners that securely affix together the portions of the fanshaft housing 306.

In one embodiment, construction of the fanshaft housing 306 forms an interior cavity 320, which encapsulates various components therein, and which is fluidly sealed using one or more seals 322 such as lip seals, gaskets, and related devices that are receptive to rotation of the shafts (e.g., the evaporator shaft 302 and the condenser shaft 304) while also providing a leak-proof seal for retaining the lubricating fluid therein. The seals in the present example include an evaporator seal 324 and a condenser seal 326 disposed proximate, respectively, the evaporator end 308 and the condenser end 310. The components include bearings 328 such as the evaporator bearings 330 and the condenser bearings 332 that are depicted in the example of FIG. 3. Other components including additional bearings, bushings, spacers, fasteners, and the like can also be incorporated in the general construction of the fanshaft 300. While such supplemental components are not necessarily discussed in detail herein, the use of these additional components may be required by the design and/or the operative characteristics of the fanshaft 300, particularly when implemented in the transportation refrigeration unit 200 of FIG. 2.

In addition to the components described above, access to the interior cavity 320 is provided via one or more plugs 334, which can be removable such as to permit lubricating fluid to be injected into the interior cavity 320. The interior cavity 320 is likewise configured to house a coupling mechanism 336, which in one example is useful to engage and disengage the evaporator shaft 302 from the condenser shaft 304. The coupling mechanism 336 includes a clutch device 338 compatible with the lubricating fluid disposed in the interior cavity 320. Components of the clutch device 338 can vary as per the implementation of, e.g., the fanshaft 220 in the transportation refrigeration unit 200 of FIG. 2.

By way of example, but not limitation, the clutch device 338 includes a coil 340, a clutch pack 342, and assorted components such as a clutch bearing 344. In one embodiment, one or more input wires 346 are incorporated into the fanshaft 300 such as by providing sealed openings 348 in the fanshaft housing 306 through which such wires are secured in communication with, e.g., the coil 340. The clutch device 338 is generally compatible with immersion in the lubricating fluid. In one example, components can be consistent with electromagnetic clutches, wherein components such as the coil 340 and/or clutch pack 342 are responsive to an input such as current from a power supply (not shown).

When implemented as part of, e.g., the power transfer mechanism 218 of FIG. 2, the clutch device 338 can operate in a number of states, including an engaged state and a disengaged state. Selection of the state is typically responsive to application of input current, wherein in one example energizing the coil 340 can cause engagement (or disengagement) of clutch device 338. The change in state can, in turn, modify the operation of the transportation refrigeration unit (e.g., units 200) by way of engaging or disengaging the evaporator shaft 302 from the condenser shaft 304.

In view of the foregoing, operation of the fanshaft housing 300 can be effectuated by feed back and related system inputs. This feedback can be in the form of sensor data, which can indicate when frost build-up on the evaporator coils has varied from some pre-determined threshold such as temperature. In another example, the feedback can be in the form of one or more pre-programmed and/or pre-determined shut offs initiated by other control structure incorporated in, or related to the transportation refrigeration unit.

It is contemplated that numerical values, as well as other values that are recited herein are modified by the term “about”, whether expressly stated or inherently derived by the discussion of the present disclosure. As used herein, the term “about” defines the numerical boundaries of the modified values so as to include, but not be limited to, tolerances and values up to, and including the numerical value so modified. That is, numerical values can include the actual value that is expressly stated, as well as other values that are, or can be, the decimal, fractional, or other multiple of the actual value indicated, and/or described in the disclosure.

While the present invention has been particularly shown and described with reference to certain exemplary embodiments, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the invention as defined by claims that can be supported by the written description and drawings. Further, where exemplary embodiments are described with reference to a certain number of elements it will be understood that the exemplary embodiments can be practiced utilizing either less than or more than the certain number of elements. 

1. In a transportation refrigeration unit of the type for conditioning the environment interior of the trailer, said transportation refrigeration unit including an evaporator fan, a condenser fan, and a power transfer mechanism for simultaneously driving the evaporator fan and the condenser fan, the power transfer mechanism further comprising: a primary fan shaft coupled to the condenser fan; a secondary fan shaft aligned with the primary fan shaft, the secondary fan shaft coupled to the evaporator fan; a coupling mechanism coupling the primary fan shaft and the secondary fan shaft; a fanshaft housing in surrounding relation to the coupling mechanism; and a lubricating fluid disposed in the fanshaft housing.
 2. A transportation refrigeration unit according to claim 1 further comprising a drive pulley in axial engagement with the primary fan shaft, wherein the coupling mechanism is operatively configured to transfer rotation of the drive pulley to the secondary fan shaft.
 3. A transportation refrigeration unit according to claim 1 wherein the fan shaft housing has a evaporator end for receiving the secondary shaft and a condenser end for receiving the primary shaft, wherein each of the evaporator end and the condenser end have an axial seal, and wherein the axial seals retain the lubricating fluid in the fanshaft housing.
 4. A transportation refrigeration unit according to claim 1 wherein the coupling mechanism comprise an electromagnetic clutch.
 5. A transportation refrigeration unit according to claim 1 further comprising an input device coupled to the coupling mechanism, wherein the coupling mechanism changes state in response to an input from the input device.
 6. A transportation refrigeration unit according to claim 1 wherein the power transfer mechanism is coupled to an internal combustion engine.
 7. A transportation refrigeration unit according to claim 6 wherein the coupling mechanism operates in a plurality of states, and wherein at least one of the states disengages the evaporator fan from the internal combustion engine.
 8. A transportation refrigeration unit according to claim 1 wherein the fanshaft housing comprises at least two portions coupled together to form an interior cavity, and wherein the coupling mechanism is disposed in the interior cavity so as to be immersed in the lubricating fluid.
 9. A power transfer mechanism for use on a transportation refrigeration unit of the type for conditioning the environment interior of the container, the transportation refrigeration unit including an evaporator fan and a condenser fan, said power transfer mechanism comprising: a coupling mechanism coupling a condenser fan shaft and an evaporator fan shaft, the condenser fan shaft coupled to the condenser fan and imparting rotation to the evaporator fan shaft through the coupling mechanism; and a fanshaft housing comprising a first portion and a second portion coupled together in a manner forming a interior cavity about the coupling mechanism, wherein the interior cavity is sealed so as to maintain a volume of a lubricating fluid therein, and wherein the coupling mechanism is immersed in the lubricating fluid.
 10. A power transfer mechanism according to claim 9 further comprising a pulley secured to the condenser fan shaft.
 11. A power transfer mechanism according to claim 9 further comprising: a first bearing device engaging the evaporator fan shaft, and a second bearing device engaging the condenser fan shaft, wherein each of the first and second bearing devices are encapsulated by the interior cavity.
 12. A power transfer mechanism according to claim 9 further comprising a seal coupled to each of the first portion and the second portion, wherein the seals retain the lubricating fluid in the interior cavity.
 13. A power transfer mechanism according to claim 9 wherein the coupling mechanism comprises an electromagnetic clutch.
 14. A power transfer mechanism according to claim 9 wherein the coupling mechanism is operatively configured to disengage the condenser fan shaft from the evaporator fan shaft in response to an input, and wherein the input indicates frost build-up on a portion of the transportation refrigeration unit.
 15. A transportation refrigeration unit comprising: a vapor compression refrigeration system comprising a compressor, an evaporator with an evaporator fan, and a condenser with a condenser fan; and a fanshaft comprising a first shaft secured to the evaporator fan, a second shaft secured to the condenser fan, and a fanshaft housing in surrounding relation to an integrated coupling mechanism communicating rotational motion between the first shaft and the second shaft, wherein the fanshaft housing forms a interior cavity about the integrated coupling mechanism, and wherein the interior cavity is sealed so as to maintain a lubricating fluid therein.
 16. A transportation refrigeration unit according to claim 15 wherein the integrated coupling mechanism comprises a clutch device disposed in the interior cavity, and wherein the clutch device communicates with one or more of the first shaft and the second shaft to disengage the condenser fan from the evaporator fan.
 17. A transportation refrigeration unit according to claim 16 wherein the clutch device is an electromagnetic clutch immersed in the lubricating fluid.
 18. A transportation refrigeration unit according to claim 15 further comprising a power transfer mechanism rotating the condenser fan, wherein the power transfer mechanism is coupled to an internal combustion engine.
 19. A transportation refrigeration unit according to claim 18 wherein the power transfer mechanism includes a pulley disposed in axial engagement with the condenser fan.
 20. A transportation refrigeration unit according to claim 15 wherein the coupling mechanism is responsive to feed back indicating frost build-up on the evaporator. 